1. Technical Field
The present disclosure relates to a continuous delta-sigma modulator for supporting multi-mode, and more specifically, to a continuous delta-sigma modulator operating in multi-mode by using a loop filter capable of order conversion.
2. Related Art
The delta-sigma modulation scheme is an analog-to-digital or a digital-to-analog conversion scheme derived from a delta modulation scheme. It is used for wireless communication systems such as a 3GPP (third generation partnership project) long term evolution (LTE) system or a worldwide interoperability for microwave access (WiMax) system due to its anti-aliasing characteristics and high signal-to-noise (SNR) ratio.
The principle of delta-sigma modulation lies in predicting of a signal, deriving an error of the signal, and correcting the error using the cumulative error. According to this, when the cumulative error is finite, an average of an input signal and an average of an output signal may become equal. Meanwhile, a delta-sigma modulator used in a receiving end of a transmission and reception system is applied to various communication systems due to its noise shaping characteristics. However, such the modulator is generally limited in operation with only a single signal bandwidth and a single clock frequency due to design complexity and difficulty in maintaining stability.
For example, a global system for mobile communication (GSM) system that requires a high SNR in a narrow bandwidth and a universal mobile telecommunications system (UMTS) that requires a medium SNR in a wide bandwidth should use delta-sigma modulators having different structures and orders. Therefore, since different modulators should be implemented according to the system, the size and power consumption of the system increase.